The Trentos were the first ships designed specifically to the limitations of the Washington Naval Treaty. This limited cruisers to 10,000 tons and 8 inch (203 mm) guns, a limitation that made firepower, speed and protection difficult to build into a single design. A particular problem faced by the Italian designers was that their ships had to be able to protect the lengthy Italian coastline from widely separated naval bases, meaning that high speed was a key feature. In the end they chose to sacrifice armor and fuel storage, and thus range, in order to attain the required speed and weight while still being armed with the latest 8 inch (203 mm) guns.

Trento started construction in 1925 along with her sister ship, Trieste. Trieste was launched first in 1926 and commissioned in 1928, while Trento followed in 1927 and 1929 respectively. A third, Bolzano, started construction in 1930 and was commissioned in 1933; the Bolzano was quite different from the other two vessels, and sometimes it is considered a class on its own. It was later concluded that the tradeoff in armour put the ships at a disadvantage, and an up-armored version of the design was produced as the highly rated Zara class in the early 1930s. The three warship constituted Italian Navy's Third Division of cruisers.

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Trieste served as the flagship of the 3rd Division. In 1940, she participated in the battle of Cape Spartivento. At Spartivento, the three cruisers of the class fired on their British counterparts from a range of 21500 yards (over 12 miles), and it is believed that either Trieste or Trento hit the heavy cruiser HMS Berwick twice and straddled HMS Manchester.[1]

On 21 November 1941 she was hit by a torpedo from the submarine HMS Utmost, and although badly damaged, she was able to reach base at Messina with difficulty. She remained out of action until mid-1942, when she rejoined the fleet. On 10 April 1943, she sank after being hit by several bombs dropped by USAAFB-24s while in port at La Maddalena, Sardinia. After the war, she was sold to Spain in 1951, being raised and moved to Ferrol in anticipation of being converted into an aircraft carrier, but a change in leadership of the Spanish Navy saw the project being dropped, and the cruiser was scrapped.[2]

In June 1929, Trento began a cruise to South America which extended until 10 October 1929. In February 1932 Trento was sent to Tianjin, China, to join the San Marco Battalion as a show of force during the Second Sino-Japanese War, returning on 30 June. In August 1933, Trento joined the Trieste and newly commissioned Bolzano to become the Second Naval Division. In 1934 the Regia Marina was re-organized, and the three ships became the Third Naval Division.

On the morning of 15 June 1942 Trento was navigating in a battle fleet to prevent a large Allied convoy from reaching Malta (Operation Vigorous), and was attacked and sunk after being torpedoed twice. The first hit was inflicted by a Malta-based Bristol Beaufort bomber at 5:15am.This plane was flown by f/o Arthur Aldridge and his crew. This operation was later recalled in his book 'The Last Torpedo Flyers' published in 2013. Trento was immobilized and left behind, assisted by the destroyer Da Verrazzano, while the rest of the fleet continued south in pursuit of the Vigorous convoy. The Royal Navy submarine HMS Umbra found the smoking ship at 9:10am, and torpedoed her hitting the magazine, sinking the Trento rapidly (9:15am). Crew members had little time to put on life vests and abandon ship. Over half the crew died from the explosions, went down with the ship or were killed when Italian escort ships dropped depth charges to stop the submarine.[citation needed]Trento still lies at the bottom of the Ionian Sea, where the Mediterranean is at its deepest, at the position 36°10′N18°40′E﻿ / ﻿36.167°N 18.667°E﻿ / 36.167; 18.667.

Bolzano was built a year later than the other two, with enough differences that she is sometimes considered a separate class. She served in most of the same missions as her sisters. She was hit three times by six-inch rounds from the British cruiser HMS Neptune in the battle of Calabria, where she sustained two deaths and minor damage below the waterline, which was patched up in just six minutes. Another round hit in the "B" turret and holed the guns, which continued to fire undeterred. A third round struck the torpedo room, where the two fatalities took place.[3] At the beginning of the battle of Spartivento, her Ro.43floatplane was the first to spot the British fleet 20 miles off Algeria.[4] On 25 August 1941, while returning from an abortive attempt to intercept minelayerHMS Manxman, used by the British in re-supply missions, Bolzano was damaged by a torpedo from the British submarine HMS Triumph near the Straits of Messina. With her steering damaged, she had to be towed to Messina. Repairs lasted three months, during which she was hit during an air raid.[5]

In August 1942, when her participation in the interception of the Pedestal convoy had been cancelled, she was again torpedoed while returning to base. Bolzano and the light cruiser Muzio Attendolo were both seriously damaged by torpedoes from the British submarine HMS Unbroken off the Aeolian Islands on 13 August.[5] The damage to Bolzano required her magazines to be flooded and she was beached at the island of Panarea. After a month, she was salvaged and taken first to Naples, then to La Spezia for repairs. While she was at La Spezia in September the Italians surrendered and she was captured by the Germans. However the damage was so heavy that they didn't have resources to repair her. She was sunk by former members of Decima Flottiglia MAS, transported by human torpedoes, in a combined Italian and British raid on 21 June 1944.[6] After the war she was refloated, and sold for scrap in 1947.